October 2017 - ghc-tickets

Re: [GHC] #7860: Add more bit fiddling functions to 'integer-gmp'
by GHC 16 Oct '17

16 Oct '17

#7860: Add more bit fiddling functions to 'integer-gmp' -------------------------------------+------------------------------------- Reporter: lebedev | Owner: hvr Type: feature request | Status: new Priority: normal | Milestone: 8.4.1 Component: Core Libraries | Version: 7.6.3 Resolution: | Keywords: integer-gmp Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #3489, #9835 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel <hvr@…>): In [changeset:"6cc232ae925bc6fc88229d96589a851068a9cace/ghc" 6cc232ae/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="6cc232ae925bc6fc88229d96589a851068a9cace" Implement {set,clear,complement}BitBigNat primitives This implements the missing `{set,clear,complement}BitBigNat` primitives and hooks them up to `Natural`'s `Bits` instance. This doesn't yet benefit `Integer`, as we still need "negative" `BigNat` variants of those primitives. Addresses #7860 (partly) Reviewed By: bgamari Differential Revision: https://phabricator.haskell.org/D3415 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7860#comment:21> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14355: Improvement of lazy evaluation
by GHC 16 Oct '17

16 Oct '17

#14355: Improvement of lazy evaluation -------------------------------------+------------------------------------- Reporter: vanto | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Hello, consider the following example:\\ {{{ Prelude> let d = (\x y -> (+)) Prelude> :t d d :: Num a => p1 -> p2 -> a -> a -> a }}} and calculating these expressions:\\ example 1:\\ {{{ Prelude> d (/) ({-# LANGUAGE TypeNTypes #-}) 1 6 Prelude> d ((\x y -> 1/0)2 3) (\x y -> 1/0) 6 3 Prelude> d 1 2 3 4 Prelude> d 'e' 'r' 5 6 Prelude> d [1] [5] 1 1 Prelude> d (1/0) (1/0) 1 0 Prelude> d (1 `div` 0) 5 3 2 Prelude> d (0/0) (0/0) 1 0 Prelude> d undefined undefined 1 0 Prelude> d True False 1 2 Prelude> d otherwise otherwise 4 3 Prelude> d maybe maybe 8 9 Prelude> d Nothing Nothing 0 7 Prelude> d EQ EQ 4 5 Prelude> d (+) (+) 0 9 Prelude> d error error 1 2 Prelude> d interact interact 1 3 Prelude> d min max 6 4 Prelude> d (:) (:) 7 3 Prelude> d foldl foldr 1 7 }}} and this:\\ example 2:\\ {{{ Prelude> d _ _ 1 2 Prelude> d a z 3 5 Prelude> d (\x -> (*/*)) (\x -> (*/*)) 2 7 Prelude> d (otherwise/otherwise) 2 6 4 }}} and this:\\ example 3: {{{ Prelude> d (/) ({-# #-}) 1 6 }}} Are the results correct? Yes. Is this consistent with common sense? No. Here again, it does not make sense. No comment, I hope this is clear to everyone.\\ Example 2 should provide a result as an example 1. it makes sense.\\ See example 3. A result with warning. you understand? Those who do not understand can close the ticket. Others can re-open the ticket, think better and improve. Do not waste your time answering me that you do not agree. This is only another idea to improve lazy evaluation. Of course, I will not make a proposal. Thank you. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14355> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4020: Please consider adding support for local type synonyms
by GHC 16 Oct '17

16 Oct '17

#4020: Please consider adding support for local type synonyms -------------------------------------+------------------------------------- Reporter: nr | Owner: (none) Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 6.12.2 checker) | Resolution: | Keywords: type synonym Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by Iceland_jack): * cc: Iceland_jack (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4020#comment:13> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14354: Unexpected type inference behavior with -XTypeApplications
by GHC 16 Oct '17

16 Oct '17

#14354: Unexpected type inference behavior with -XTypeApplications -------------------------------------+------------------------------------- Reporter: mbw | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: | Operating System: POSIX Architecture: x86_64 | Type of failure: None/Unknown (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In the following snippet, type inference of the let bound identity function after applying a type unexpectedly fails: {{{#!hs GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help [...] *Main> :set -XTypeApplications *Main> :t id @Int id @Int :: Int -> Int *Main> let the = id *Main> :t the @Int <interactive>:1:1: error: • Cannot apply expression of type ‘a0 -> a0’ to a visible type argument ‘Int’ • In the expression: the @Int *Main> :t _ @Int }}} Note that it works with `id`, but not with `the`. I would expect to be able to write something like `the @Double 42`, for instance. For completeness' sake and since I don't know if it is related or relevant, with GHC 8.0.2, a panic is easily triggered: {{{#!hs Prelude> :set -XTypeApplications Prelude> :t _ @Int ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): initTc: unsolved constraints WC {wc_insol = [W] __a15d :: t_a15c[tau:3] (CHoleCan: _)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} This however does not happen with GHC 8.2.1. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14354> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4020: Please consider adding support for local type synonyms
by GHC 15 Oct '17

15 Oct '17

#4020: Please consider adding support for local type synonyms -------------------------------------+------------------------------------- Reporter: nr | Owner: (none) Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 6.12.2 checker) | Resolution: | Keywords: type synonym Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by mentheta): * cc: mentheta (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4020#comment:12> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13875: ApplicativeDo desugaring is lazier than standard desugaring
by GHC 15 Oct '17

15 Oct '17

#13875: ApplicativeDo desugaring is lazier than standard desugaring -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.3 Keywords: ApplicativeDo | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Suppose I write {{{#!hs import Data.Maybe (isJust) bangy m = do (_,_) <- m return () main = print $ isJust (bangy (Just undefined)) }}} If I compile this with `ApplicativeDo`, it prints `True`. Otherwise, it throws an exception. The basic problem is that the (correct) `bangy` function ''requires'' a `Monad` constraint, but `ApplicativeDo` replaces it with a lazier function that can get by with `Functor`. I believe it should desugar correctly, and impose a `Monad` constraint here. To get the `Functor` constraint should require an explicit lazy pattern match: {{{#!hs bangy m = do ~(_,_) <- m return () }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13875> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12822: Cleanup GHC verbosity flags
by GHC 14 Oct '17

14 Oct '17

#12822: Cleanup GHC verbosity flags -------------------------------------+------------------------------------- Reporter: hsyl20 | Owner: Type: task | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple newcomer,flags | Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- 1) In the discussion of Phab:D2679#77898, Simon Marlow suggested that we make verbosity levels (`-v0`, `-v1`...) work just like optimization levels (`-O0`, `-O1`...), i.e., that we make each verbosity level a collection of verbosity flags. Currently the verbosity level is tested against explicitly in several places in GHC's code. 2) Homogenize verbosity flags: currently, flags that change GHC's reporting have various prefixes: - `-fprint-*` - `-fshow-*` - `-dshow-passes` - `-ddump-*` - `-dppr-*` - `-dverbose-*` Maybe we should homogenize (some of) them by using a common `-v` prefix as in `-vshow-source-paths`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12822> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14352: Higher-rank kind ascription oddities
by GHC 14 Oct '17

14 Oct '17

#14352: Higher-rank kind ascription oddities -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: TypeInType | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC accepts these two definitions: {{{#!hs {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeInType #-} module Bug where import Data.Proxy f :: forall (x :: forall a. a -> Int). Proxy x f = Proxy g :: forall (x :: forall a. a -> Int). Proxy (x :: forall b. b -> Int) g = Proxy }}} However, it does not accept this one, which (AFAICT) should be equivalent to the two above: {{{#!hs h :: forall x. Proxy (x :: forall b. b -> Int) h = Proxy }}} {{{ GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug.hs, interpreted ) Bug.hs:13:23: error: • Expected kind ‘forall b. b -> Int’, but ‘x’ has kind ‘k0’ • In the first argument of ‘Proxy’, namely ‘(x :: forall b. b -> Int)’ In the type signature: h :: forall x. Proxy (x :: forall b. b -> Int) | 13 | h :: forall x. Proxy (x :: forall b. b -> Int) | ^ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14352> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14351: reverse-errors doesn't affect instance errors
by GHC 13 Oct '17

13 Oct '17

#14351: reverse-errors doesn't affect instance errors -------------------------------------+------------------------------------- Reporter: br1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In the following sample code, the errors are in the same order with and without -freverse-errors: {{{ data Foo = Foo data Bar = Bar instance Show (Foo Int) instance Read (Bar Int) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14351> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14348: Poly-kinded definitions silently introduce extra type arguments captured by TypeApplications
by GHC 13 Oct '17

13 Oct '17

#14348: Poly-kinded definitions silently introduce extra type arguments captured by TypeApplications -------------------------------------+------------------------------------- Reporter: gallais | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The first type argument of a poly-kinded definition is not the one explicitly quantified over in the definition but rather the implicitly inserted kind. This leads to the puzzling error message "Expected a type, but ‘a’ has kind ‘k’" when ghc actually expected a kind. {{{#!haskell {-# LANGUAGE GADTs, PolyKinds, ScopedTypeVariables, TypeApplications #-} data EQ :: k -> k -> * where Refl :: EQ a a data Wrap (a :: k) = Wrap (EQ a a) wrap :: forall (a :: k). Wrap a wrap = Wrap @a Refl -- fails -- wrap = Wrap @k @a Refl -- works }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14348> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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